Control device for preventing red-eye effect on camera

ABSTRACT

A camera capable of operating in a red-eye prevention mode. The camera has an electronic flash device which is activated by a drive circuit in synchronization with the exposure. The electronic flash device also serve as a pre-light-emission device capable of performing pre-light-emission for the purpose of preventing red-eye effect. When it is judged from the photographing condition that red-eye effect may occur, a controller activates the electronic flash device to effect a pre-light-emission for reducing the size of pupils of eyes of a person to be photographed, before the main flashing which is executed in synchronization with the exposure.

This is a continuation of application Ser. No. 08/486,505 filed Jun. 7,1995 (abandoned), which is a division of application Ser. No. 08/071,613filed Jun. 4, 1993, which is a continuation of application Ser. No.07/974,512 filed Nov. 12, 1992 (abandoned), which is a division ofapplication Ser. No. 07/930,466 filed Aug. 20, 1992 (abandoned), whichis a continuation of application Ser. No. 07/785,210 filed Oct. 25, 1991(abandoned), which is a continuation of application Ser. No. 07/632,648filed Dec. 26, 1990 (abandoned), which is a continuation of applicationSer. No. 07/445,996 filed Dec. 4, 1989 (abandoned), which is acontinuation-in-part of application Ser. No. 07/323,386 filed Mar. 14,1989 (abandoned).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a control device for use on a cameraand capable of preventing red-eye effect which tends to be caused in aflash-assisted color photography.

2. Related Background Art

The red-eye effect is a phenomenon in which human eyes are red- orgold-colored in a flash-assisted color photography. This phenomenon isattributable to a fact that the flash light from an electronic flash isapplied to and reflected by the retinas through the pupils of human eyesto reach the photographic film. As is well known, numerous capillaryblood vessels exist around the retinas to circulate blood containinghemoglobin which is red, so that the image formed by the light reflectedfrom the retinas inevitably becomes red.

Experience shows that the red-eye effect is remarkable particularlyunder the following conditions:

1) When the photographing environment is dark

The size of the pupil of the human eye varies depending on thebrightness of the environment. For instance, the pupil is expanded toabout 7 to 8 mm in diameter in the dark. In such a case, the quantity ofthe light incident to the eye and the quantity of the light reflected bythe retina are increased, with the result that the red-eye effect isenhanced correspondingly.

2) When the distance between the light-emitting portion of theelectronic flash and the photographing optical axis is small

The retina of a human eye generally has a high reflection factor andexhibits a high directivity of the reflected light. Therefore, thered-eye effect is enhanced when the three elements, i.e., thelight-emitting portion, photographing lens and the eye, are located inrelation to one another such that the light reflected from the retinacan easily come into the photographing lens, i.e., when thelight-emitting portion of the electronic flash is located close to theoptical axis of the photographing lens. More particularly, the red-eyeeffect is produced without fail when the angle formed between a lineinterconnecting the eye of a person as the photographing object and thephotographing lens and a line interconnecting the eye and thelight-emitting portion of the electronic flash is smaller than apredetermined angle. Experience shows that this angle generally rangesbetween about 2 and 2.5 degrees. Thus, the red-eye effect would beavoided if the light-emitting portion of the electronic flash is spacedapart from the optical axis of the photographing lens. The distance,however, is practically limited because of the restriction in thedistance between the camera and the object (this distance will bereferred to as "object distance" hereinafter). Thus, the red-eye effectmay be unavoidable under the circumstance in which the object distanceis greater than a certain value.

Under these circumstances, methods have been proposed for avoiding theundesirable red-eye effect. For instance, "psa JOURNAL", July, 1952discloses a method in which the person to be photographed is kept in abright condition in advance of the photographing so that the state ofthe eyes is changed to cope with the brightness, and the flash lights upwhen the pupil diameter has come down below 3 mm, whereby the red-eyeeffect can be suppressed.

On the other hand, Japanese Patent Publication No. 58-48088 discloses anart in which pre-light-emission is conducted before the photographingover a period necessary for the pupil to reduce its diameter and, whenthe pupil diameter has been minimized, the flashing section of theelectronic flash operates to enable photographing.

Japanese Patent Publication No. 58-9130 discloses an art in which a pairof flash discharge tubes are used such that pre-light-emission iseffected by one of these two tubes so as to reduce the pupil diameterand then main-flash is generated by the other tube to enable thephotography.

These known methods, however, suffer from various disadvantages asfollows.

A first disadvantage is as follows. When pre-light-emission is effectedfor the purpose of preventing red-eye effect, shutter release with mainflash is delayed over a period necessary for the pupil to contract,typically 0.75 second. Therefore, in a camera which is designed toeffect the pre-light-emission, the pre-light-emission is wastefullyeffected even in photography under a bright condition and even in thecase where the pupil has contracted as in the case of the second and thefollowing shots in continuous flash-assisted photography in thedarkness. In consequence, the photographer may lose the best photoopportunity. In addition, power of the batteries used for thepre-light-emission is wastefully consumed.

A second disadvantage is that, when the power supply or batteries havenot been charged sufficiently both for the pre-light-emission and mainflashing, there is a risk for the photographer to lose a photoopportunity because of shortage of the electric charge as a result ofthe discharge for the pre-light-emission.

A third disadvantage is that the pre-light-emission is effective onlywhen the person to be photographed correctly looks at the camera,because the light generated by the pre-light-emission cannot enter theeyes if the eyes do not sight in the direction of the camera. Inaddition, the person to be photographed tends to mis-understand that thephotography is finished upon completion of the pre-light-emission sothat he may turn his head or close his eyes when photographed, with theresult that the intended shot fails.

A fourth problem is caused by the fact that the intensity of the lightgenerated in the pre-light-emission is constant regardless of the objectdistance, so that the quantity of light received by the eyes variesdepending on the object distance. A too small object distance may causethe face to be unnaturally changed or the eyes to be closed due todazzle. Such an excessively large quantity of pre-light-emission lightreceived by the eyes is nothing but a wasteful use of the battery power.

A fifth problem is that there are some persons whose pupils do notsufficiently contract by a single pre-light-emission, so that thered-eye effect cannot be suppressed satisfactorily because the knownmethod conducts pre-light-emission only once in advance of the shot.

A camera is known in which, as disclosed in the specification of theU.S. Pat. No. 4,305,647, an electronic flash is activated forpre-light-emission in advance of the shutter release which isaccompanied by the main flashing, and the light reflected from theobject is measured. The measured value representing the objectbrightness is used as data for determining the aperture value or as datafor judging whether the pre-set aperture value is adequate, with analarm activated when the aperture value is judged as being inadequate.

When the pre-light-emission for preventing red-eye effect is applied tothis type of camera, pre-light-emission is conducted twice: namely, oncefor determination of the aperture value and once for preventing thered-eye effect. In consequence, battery power is consumed rapidly andthe person to be photographed is confused by the repetition of flashing.

A camera also is known which is capable of conducting a timer-assistedphotography. In this type of camera, the timer starts to measure thetime in response to full pressing of a release button and releases theshutter when a predetermined set time has passed. In most cases, thetimer-assisted photographing mode is used when the photographing objectis a person or persons. This means that the red-eye effect tends to beexperienced frequently in the timer-assisted photography.

The camera having the timer function, when incorporating a flash forpreventing red-eye effect, requires that the photographing mode beswitched to select the pre-light-emission mode by, for example, pressinga push button, when the timer-assisted photography is to be conducted.Such a switching operation is troublesome and the red-eye effect tendsto be caused when the switching has failed.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a red-eyeeffect prevention device for a camera, which allows thepre-light-emission to be omitted when the red-eye effect preventionfunction is not needed and which minimizes the wasteful use of thebattery power.

Another object of the present invention is to provide a red-eye effectprevention device for a camera, in which the pre-light-emission for thepurpose of preventing generation of red-eye effect is omitted when themain flash device has not been charged to a degree enough for theflashing, thus enabling photography for the desired shot without fail.

Still another object of the present invention is to provide a red-eyeeffect prevention device which is capable of informing the person to bephotographed of the fact that the photography with main flashing iseffected following a pre-light-emission.

A further object of the present invention is to provide a red-eye effectprevention device which provides a constant quantity ofpre-light-emission light received by eyes regardless of the objectdistance, thereby optimizing the light stimulus on the human eyes.

A still further object of the present invention is to provide a red-eyeeffect prevention device which is capable of performingpre-light-emission a plurality of times, thereby avoiding red-eye effectregardless of the type of the object.

A still further object of the present invention is to provide a cameraincorporating a red-eye effect prevention device in which apre-light-emission for preventing generation of red-eye effect isconducted without fail whenever the camera operates in a timer-assistedmode, thus eliminating troublesome switching operation, as well asgeneration of red-eye effect which is unavoidable in some of knowncameras when the switching has been forgotten.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a first embodiment of the presentinvention;

FIGS. 2 and 3 are flow charts showing a main routine;

FIG. 4 is an illustration of a positional relationship between a cameraand a pupil of a person to be photographed;

FIGS. 5 to 7 are flow charts showing interrupt routines;

FIGS. 8 to 10 are flow charts of different modifications of the mainroutine;

FIGS. 11 to 14 are flow charts showing different modifications ofinterrupt routines;

FIG. 15 is a circuit diagram of a modification of a pre-light-emissiondevice;

FIG. 16 is a flow chart of a modification of the interrupt routine;

FIG. 17 is a flow chart showing a modification of the main routine;

FIG. 18 is a flow chart showing a modification of the interrupt routine;

FIG. 19 is a time chart showing the relationship between repetition ofpre-light-emission and pupil size;

FIG. 20 is a flow chart showing a modification of the interrupt routine;

FIG. 21 is a graph showing the relationship between pre-light-emissioncondition and pupil size;

FIG. 22 is a flow chart showing a modification of the interrupt routine;

FIG. 23 is a block diagram of a second embodiment;

FIG. 24 is a flow chart showing the main routine;

FIG. 25 is a flowchart showing an interrupt routine;

FIG. 26 is a block diagram of a third embodiment;

FIG. 27 is a flow chart showing a main routine;

FIG. 28 is a perspective view of a switch device;

FIGS. 29A and 29B are perspective views of modifications of the switchdevice;

FIG. 30 is a block diagram showing a fourth embodiment of invention;

FIG. 31 is a circuit diagram of a display driver;

FIG. 32 is a time chart showing the signal levels at the terminals shownin FIG. 32;

FIG. 33 is a flow chart showing the procedure of the main routine;

FIG. 34 is a flow chart showing the procedure of the interrupt routine;

FIG. 35 is a circuit diagram of the display driver in a modification ofthe above embodiment;

FIG. 36 is a time chart showing the signal levels at the terminals shownin FIG. 35;

FIG. 37 is a flow chart showing the procedure of the main routine;

FIG. 38 is a flow chart showing the procedure of the interrupt routine;

FIG. 39 is a circuit diagram of the display driver in anothermodification;

FIG. 40 is a flow chart showing the procedure of the main routine;

FIGS. 41A and 41B show examples of display by means of 7-segment LEDdisplay elements; and

FIG. 42 is a flow chart showing the procedure of the main routine;

DESCRIPTION OF THE PREFERRED EMBODIMENT

A first embodiment of the present invention will be described withreference to FIG. 1.

A lens drive circuit 2, a focus detection circuit 3, a photometeringcircuit 4 and a camera control circuit 5 are connected to a CPU 1through signal transmission lines BL1. The focus detection circuit 3has, for example, a pair of light-receiving elements such as CCDs. Apair of object images are formed on these elements through an exposurelens LE and a pair of lenses which are not shown. Upon receivingelectrical signals from these elements, the focus detection circuitdelivers a focus detection signal which represents the amount of offsetof the object image forming plane and a predetermined image formingplane, as well as the direction of the offset.

The photometering circuit 4 has a light receiving element which receiveslight from the object and is capable of producing an output which isdelivered as photometric data to the CPU.

The camera control circuit 5 is connected to an exposure control device6 capable of controlling aperture and shutter and also to a displaydevice 7 such as a liquid crystal display device. The camera controlcircuit 5 is capable of operating in accordance with instructions givenby the CPU so as to enable the display device 7 to display informationconcerning photography such as the exposure value, shutter speed and soon, and to drive the exposure control device 6 thereby effectingexposure.

The lens drive circuit 2 includes a motor 9 for driving a focusing lens8. The motor 9 is driven in accordance with a lens driving instructionfrom the CPU 1 so as to drive the focusing lens, thereby conductingfocusing. The lens drive instruction is generated by the CPU inaccordance with the above-mentioned focus detection signal.

An electronic flash device 10 and a pre-light-emission device 11integral with the electronic flash device 10 are connected to the CPU.

The electronic flash device 10 includes a xenon discharge tube XE1, amain capacitor 101 for storing electric charges for activating the xenondischarge tube XE1, a charging circuit 102 for charging the maincapacitor 101, and a discharge circuit 103 for controlling the start andtermination of light emission, i.e., the discharge, in the xenondischarge tube XE1. The charging circuit 102 produces a charge-up signal104 upon completion of the main capacitor 101 to a level high enough forallowing the discharge in the xenon light-emitting tube XE1 and deliversthis signal to the CPU. Upon receipt of this charge-up signal 104, theCPU delivers a discharge start signal 105 to the discharge circuit 103as a later-mentioned second switch SW2 is turned on. In response to thedischarge start signal 105, the discharge circuit 103 delivers theelectric charges of the main capacitor 101 to the xenon discharge tubeXE1 thereby initiating the emission of light from the xenon dischargetube XE1. The amount of light emitted by the xenon discharge tube XE1 ismeasured by an emission amount control circuit and the result ofmeasurement is delivered to the CPU as light amount data used for thepurpose of controlling the amount of light emitted from the dischargetube. As an emission termination instruction 106 is delivered by the CPUto the discharge circuit 103, the discharge circuit terminates thesupply of the electric charges to the xenon discharge tube XE1, therebyterminating the discharge from the xenon discharge tube XE1.

The pre-light-emission device 11 includes a xenon discharge tube XE2capable of emitting light in amount large enough to cause the pupils ofhuman eyes to contract, a capacitor 111, a charging circuit 112 forcharging the capacitor 111, and a discharge circuit 113 for controllingthe start and termination of the discharge in the xenon discharge tubeXE2. Upon completion of the charging of the capacitor 111 to a levelhigh enough to cause a discharge in the xenon discharge tube XE2, thecharging circuit 112 produces a charge-up signal 114 and delivers thesame to the CPU. Upon receipt of the charge-up signal 114, the CPUdelivers a discharge start instruction 115 to the discharge circuit 113as the second switch is turned on, so that the discharge circuit 113delivers electric charges of the capacitor 111 to the xenon dischargetube XE2 thereby allowing the tube to emit pre-light-emission light. TheCPU also delivers a discharge termination instruction 116 to thedischarge circuit 113, thereby terminating the pre-light-emission.

A release switch SW operatively associated with a release button (notshown) is connected to the CPU. The release switch SW is composed of afirst switch SW1 and the aforementioned second switch SW2. Thearrangement is such that the first switch SW1 is turned on in responseto pressing of the release button to the bottom of a first stroke and,as the release button is further pressed to the bottom of the secondstroke, the second switch SW2 is turned on. In response to the turningon of the first switch SW1, the CPU activates the above-mentioned focusdetection circuit 3 and the photometering circuit 4, and determines thedistance between the camera and the object in accordance with the focusdetection signal derived from the focus detection circuit 3, as well asthe amount of drive of the lens for bringing the focusing lens 8 to thebest-focus state. Then, a lens drive instruction is delivered to thelens drive circuit 2 in order to drive the focusing lens to thebest-focus position, in accordance with the lens driving amount computedby the CPU.

The turning on of the first switch SW1 also initiates determination ofthe object brightness B on the basis of the photometric data derivedfrom the photometering circuit 4. Then, as the second switch SW2 isturned on, the exposure control device 6 is driven to effect theexposure. In this state, the electronic flash device 10 or thepre-light-emission device 11 is activated as desired.

A voice generating circuit 14 also is connected to the CPU. The voicegenerating circuit 14 has a speaker 15 which generates voice in responseto a voice generating instruction from the CPU. The voice is for tellingthe person to be photographed that a pre-light-emission is executed inadvance of the exposure. For instance, the voice tells "Please do notmove until the flash lights twice".

The CPU determines whether the present photographing conditions maycause red-eye effect when the exposure is done with the assist of theflash light, in accordance with the object distance D and the objectbrightness. When the conditions are judged as possibly causing red-eyeeffect, the CPU produces a red-eye effect signal so as to set the camerain a red-eye effect prevention mode. Then, in response to turning on ofthe second switch SW2, a voice generating instruction is input to thevoice generating circuit 14 so as to activate this circuit and then toactivate the pre-light-emission device 11. Thereafter, a lightinginstruction is delivered to the camera control circuit 5 so as to lightthe LED 13 so as to inform the person to be photographed that exposurewith the aid of the electronic flash 10 is going to be executed. Then,when 0.75 second has passed after the operation of thepre-light-emission device 11, the LED 13 is turned off and the exposurecontrol device 6 is driven through the camera control circuit 5, therebyoutputting a discharge start signal to the discharge circuit 103. Thelighting of the LED 13 is effected after the operation of thepre-light-emission device 11 but before the operation of the electronicflash 10.

A description will be given hereinafter of the control performed by theCPU, in accordance with the flow chart.

A program shown in FIGS. 2 and 3 is started as the first switch SW1 isturned on. Referring first to FIG. 2, a memory is reset in Step S 1 toinitialize the values set therein. At the same time, all the circuitsare reset. In consequence, the focus detection circuit 3 and thephotometering circuit 4 convert the results of the detection by thelight-receiving elements and deliver the electric signals to the CPU. InStep S 2, the CPU reads the focus detection signal from the focusdetection circuit 3 and determines the object distance D in Step S 3.The process then proceeds to Step S 4.

In Step S 4, the CPU determines the amount of driving of the focusinglens 8 necessary for bringing the focusing lens 8 to a best-focusposition. In Step S 5, the focusing lens 8 is driven by the motor 9 tothe best focus position. In Step S 6, photometric data is read from thephotometering circuit 4 and, in Step S 7, the brightness B of the objectis determined in accordance with the thus obtained photometric data.Referring now to FIG. 3, in Step S 8, the time value and the aperturevalue are determined in accordance with the brightness B of the objectand the ISO sensitivity. The thus determined time value and the aperturevalue are delivered to the camera control circuit 5 in Step S 9. Thecamera control circuit 5 then operates to display these values on thedisplay device 7.

The process then proceeds to Step S 10 in which a judgment is executedas to whether the electronic flash 10 is to be used. The judgment isexecuted by detecting whether an electronic flash inhibition switch (notshown) is set for inhibiting the use of the electronic flash 10 or bydetermining whether the use of the electronic flash device 10 isnecessary on the basis of the detected brightness B of the object. Ifthe answer to the question posed in Step S 10 is YES, the CPU operatesthe charging circuit 102 so as to start the charging and then theprocess proceeds to Step S 11. Conversely, when the answer is NO, thered-eye effect prevention mode is dismissed in Step S 14 and the processreturns to Step S 2.

In Step S 11, the CPU judges whether the charging of the main capacitor101 of the electronic flash device 10 has been finished, by detectingwhether the charge-up signal has been output from the charging circuit102. If the charge-up signal has been delivered from the chargingcircuit 102, an answer YES is given in Step S 11 so that the processproceeds to Step S 12. However, if the charge-up signal has not beenproduced, i.e., if the capacitor has not been charged up, an answer NOis given so that the process proceeds to Step S 14.

In Step S 12, a judgment is executed as to whether the presentconditions may cause the red-eye effect. In this embodiment, thejudgment is executed on the basis of the object distance D and theobject brightness B.

FIG. 4 illustrates the condition for generation of red-eye effect. Asymbol P represents one of the pupils of the person to be photographed.The red-eye effect tends to occur when the angle θ, which is formedbetween a line l₁ passing through the pupil P and the center of thephotographing lens LE and a line l₂ passing through the pupil P and thecenter of the xenon flashing device 10, is 2° or below. Representing thedistance between the axes of the exposure lens LE and the xenon tube XE1by H, the angle θ is given by a formula tan θ=H/D.

From this formula, the object distance D is determined as follows:

    D=H/tanθ                                             (1).

Assuming here that the distance H between the axes of the exposure lensLE and the xenon tube XE1 of the electronic flash 10 is 0.1 m and thatthe red-eye effect is produced when the above-mentioned angle θ is 2° orbelow, the object distance D at which the red-eye effect possibly occurscan be given as follows.

    D=28.6×0.1 m=2.86 m.

Thus, the red-eye effect is considered to occur when the object distanceis 2.86 m or greater.

It will be understood that the object distance D as determined by theformula (1) can be used as the criterion for the judgment of thephotographing condition as to whether the red-eye effect will beproduced or not.

On the other hand, when the object brightness is higher than a certainlevel, there is almost no possibility for the red-eye effect to occur,because the pupils are closed almost fully. In other words, the red-eyeeffect is produced only when the object brightness is so low as to causethe pupils to open.

In this embodiment, therefore, the CPU judges that the red-eye effectmay occur when the object distance D is greater than the above-mentionedcriterion value of 2.86 m while the object brightness B is below apredetermined reference level. If these conditions are met in Step S 12,the process proceeds to Step S 13, whereas, if the conditions are notmet, the process proceeds to Step S 14. In Step S 13, the camera is setin the red-eye effect prevention mode and then the process returns toStep S 2 to repeat the described steps. The above-mentioned distance His determined by the CPU which receives a signal representative of theheightwise position of the xenon tube XE1 delivered by the electronicflash 10.

As the second switch SW2 is turned on in this state, the interruptroutine shown in FIGS. 5 to 7 is performed. Referring first to FIG. 5,in Step S 21, a judgment is executed as to whether the camera has beenset in the red-eye effect prevention mode. If the answer is YES, theprocess proceeds to Step S 22, and a discharge instruction 115 isdelivered to the pre-light-emission device 11 thereby causing the xenontube XE2 to flash so as to illuminate the person to be photographed. Inconsequence, the eyes of the person as the photographing object areilluminated with the pre-light-emission light so that the pupilscontract.

In Step S 23, a judgment is executed as to whether a predetermined time,e.g., 0.75 second, necessary for the pupil diameter to be minimized, haselapsed after the emission of the light from the xenon tube XE2. Thisjudgment is executed by starting a timer simultaneously with thedelivery of the discharge instruction to the xenon tube XE2. If theanswer is NO, the process stays on Step S 23 until the above-mentionedtime expires. Conversely, if the answer is YES, the process proceeds toStep S 24 in which the diaphragm is operated through the camera controlcircuit 5. Then, in Step S 25, the main mirror is lifted up. In Step S26, the shutter front curtain is made to run to start exposure and,thereafter, whether the electronic flash device 10 is used is judged inStep S 27.

If the answer to the question posed in Step S 27 is NO, the processproceeds to Step S 31 in which a judgment is executed as to whether apredetermined exposure time has elapsed. If the answer is NO, theprocess stays on Step S 31 until the predetermined exposure timeelapses. Conversely, if the answer is YES, the process proceeds to StepS 34 of FIG. 7 in which the rear shutter curtain is made to run therebyterminating the exposure. Then, in Step S 35, the main mirror is setdown whereby the routine is completed.

Conversely, if the answer to the question posed in Step S 27 is YES, theprocess proceeds to Step S 28 in which a judgment is executed as towhether the aperture has been fully opened. If the answer is NO, Step S28 is maintained until the aperture is fully opened. If the aperture hasbeen fully opened, a discharge start instruction is given to thedischarge circuit 103 of the electronic flash device 10 in Step S 29thereby starting flashing of the xenon tube XE1. The process thenproceeds to Step S 30 in which a judgment is executed as to whether theaperture opening time has become equal to a set synchronization time. Ifthe answer is YES, the process proceeds to Step S 34.

When the answer to the question posed in Step S 30 is NO, the processproceeds to Step S 32 which determines whether the amount of lightemitted from the xenon lamp 1 has reached a predetermined value. Thisjudgment is conducted in accordance with the photometric data which isinput from the light emit amount control circuit 12 to the CPU. If theanswer to the question posed in Step S 32 is NO, the process returns toStep S 30. However, if the answer is YES, the process proceeds to Step S33 in which a discharge termination instruction is given to thedischarge circuit 103 thereby stopping the discharge in the xenon tubeXE1. Then, the process proceeds to Step S 34. According to this routine,the flash-assisted exposure is conducted when the pupil size has beenminimized, whereby the generation of the red-eye effect is prevented.

Thus, in the process described hereinbefore, the CPU judges that thered-eye effect is possible to occur on condition that the objectdistance D as determined in Step S 3 meets the condition of θ<2° whilethe object brightness B is below a predetermined level. In such a case,the CPU operates the pre-light-emission device 11 so as to presentoccurrence of red-eye effect. When either one or both of these twoconditions are not met, the CPU does not operate the pre-light-emissiondevice 11, so that loss of photo opportunity due to unnecessarypre-light-emission is avoided and wasteful use of the battery power isprevented.

Referring to FIG. 1, a display light-emitting diode (referred to as LED)13 set in the viewfinder is connected to the camera control circuit 5.The CPU judges whether the present photographing conditions may causered-eye effect, of the basis of the object distance D and the objectbrightness B. Upon judging that the red-eye effect may occur, the CPUoperates the LED 13 through the camera control circuit 5 to make the LEDflicker, thereby informing the user of the possibility of occurrence ofthe red-eye effect.

A third switch SW3 connected to the CPU is operatively associated with amomentary type button for operating the red-eye effect preventiondevice. The third switch SW3 produces a red-eye effect preventioninstruction when it is turned on for the first time and a red-eye effectprevention dismissal instruction when turned on for the second time. Thecamera is set in the red-eye effect prevention mode in response to thered-eye effect prevention instruction and this mode is dismissed inresponse to the dismissal instruction.

FIG. 8 shows an example of the operation which is conducted when thecamera incorporates the LED 13 and the third switch SW3. The flow shownin FIG. 8 is substituted for the flow shown in FIG. 3. In this Figure,therefore, the same step Nos. are used to identify the same steps asthose in the flow shown in FIG. 3. The description therefore will befocused mainly on the features which discriminate the flow of FIG. 8from the flow of FIG. 3.

When the present photographing conditions are judged as possibly causingred-eye effect in Step S 12, the process proceeds to Step S 41 in whichthe LED 13 is made to flicker. The process then proceeds to Step S 42 inwhich a judgment is executed as to whether the red-eye effect preventioninstruction has been given by the third switch SW3 which is turned ononly when the red-eye effect prevention button is pressed. It will beseen that the third switch SW 3 alternatingly produces the red-eyeeffect prevention instruction and the red-eye effect preventiondismissal instruction each time it is turned on through the red-eyeeffect prevention button. The "on" state of the switch can be receivedeach time the camera power supply is in "on" state. The red-eye effectprevention instruction is turned off upon completion of exposure of eachframe, thereby avoiding the possibility of any unnecessarypre-light-emission.

If the answer to the question posed in Step S 42 is YES, the processproceeds to Step S 13 in which the camera is set in the red-eye effectprevention mode. The process then returns to Step S 2. Conversely, ifthe answer is NO, the process returns to Step S 2 via Step S 14 in whichthe red-eye effect prevention mode is dismissed.

According to this process, the LED 13 flickers to inform the user of thepossibility of occurrence of red-eye effect when the CPU has judged thatthe present photographing conditions have such a possibility. The userthen manipulates the button of the red-eye effect prevention device,before pressing the second switch SW2, so that a pre-light-emission isperformed by the xenon tube XE2 of the pre-light-emission device 11 inadvance of the flashing of the xenon tube XE1 of the electronic flashdevice 10. However, in case that the photographer has operated thesecond switch SW2 without turning on the button of the red-eye effectprevention device, the xenon tube XE1 of the electronic flash device 10alone flashes without being preceded by the pre-light-emission. Thephotographer therefore can select freely either the mode in which thepre-light-emission is executed and a mode in which thepre-light-emission is omitted. For instance, when no person exists inthe field of the object to be photographed, pre-light-emission isunnecessary because there is no possibility of occurrence of red-eyeeffect. In consequence, the photographer can take a photograph with goodtiming, without being disturbed by unnecessary pre-light-emission.

In the described embodiment, the CPU judges that a red-eye effect mayoccur when both the condition of the object distance D being greaterthan the value given by the formula (1) and the condition of the objectbrightness being below a predetermined level are simultaneously met.However, the possibility of occurrence of red-eye effect is still largeeven if both of these conditions are not simultaneously met, i.e., evenwhen either one of these conditions is not met. Thus, the describedembodiment may be modified such that the red-eye effect preventionfunction is put into effect when either one of these conditions is met.A modification also is possible such that whether the red-eye effect mayoccur is judged upon consultation with a table which stores the dataconcerning such a possibility on a plurality of combinations betweeneach of a plurality of sections or steps of the object distance D andeach of a plurality of sections or steps of the object brightness B.

It is also to be noted that the described embodiment can also be appliedto a camera of active range finding type in which light is projectedfrom the camera to an object and light reflected from the object isreceived by a light-receiving element which produces a detection signalto be used in the determination of the object distance, although asingle-lens reflex camera has been specifically mentioned in which theobject distance D is determined on the basis of the amount and directionof offset of the object image plane from a predetermined image formingplane on the basis of signals from a pair of light-receiving elements.

A description will be given with reference to FIG. 9 as to amodification in which the occurrence of pre-light-emission forpreventing occurrence of red-eye effect is determined on the basis ofthe state of charging of the main capacitor 101 of the electronic flashdevice 10 so as to enable omission of the pre-light-emission in theevent that the main capacitor 101 has not been charged sufficiently. Theflow shown in FIG. 9 is substituted for the flow shown in FIG. 3 and,therefore, the same step Nos. are used in FIG. 9 to indicate the samesteps as those appearing in the flow chart shown in FIG. 3.

If the use of the electronic flash device 10 is confirmed in Step S 10,the process proceeds to Step S 51 in which the charging of the maincapacitor 101 of the electronic flash device 10 is started. The processthen proceeds to Step S 12 which executes judgment as to whether thepresent photographing conditions may cause red-eye effect.

If an affirmative answer is obtained in Step S 12, charging of thecapacitor 111 of the pre-light-emission device 11 is commenced in Step S52. Subsequently, in Step (S 53, the charging circuit 102 of theelectronic flash device 10 delivers a charge completion signal and, atthe same time, a judgment is executed as to whether the charge-up signalhas been delivered by the charging circuit 112 of the pre-light-emissiondevice 11. Namely, whether both the main capacitor 101 of the electronicflash device 10 and the capacitor 111 of the pre-light-emission device11 have been charged. Upon confirming the charge-up signals from bothcharging circuits, the process proceeds to Step S 13 in which the camerais set for operation in the red-eye effect prevention mode. However, ifone of these charge-up signals is missed, the red-eye effect preventionmode is dismissed in Step S 14.

Thus, according to the flow shown in FIG. 9, the CPU judges that thered-eye effect may occur when the object distance D is greater than avalue which provides a condition of θ<2° while the object brightness Bis below a predetermined reference level. When flash-assisted exposureis to be conducted under such conditions, the CPU operates thepre-light-emission device 11 in advance of the main flash, on conditionthat both the main capacitor of the electronic flash device 10 and thecapacitor of the pre-light-emission device have been charged up. Thus,the pre-light-emission device 11 is not allowed to operate when one ofthe following states is confirmed: (1) the photographing mode is not theflash-assisted mode; (2) at least one of the capacitors has not beencharged up; and (3) the present photographing conditions are judged asnot possibly causing red-eye effect. It is to be understood, however,the flash-assisted photography can be executed by adopting the interruptroutine of FIGS. 5 to 7 which enables the xenon tube XE1 to flash, evenif the main capacitor 101 has not been charged up. The detection of thestate of charging of the capacitor of the pre-light-emission device 11is not essential. The arrangement may be such that thepre-light-emission device 11 operates regardless of the state ofcharging of its capacitor, provided that the main capacitor 101 has beencharged up.

A modification of the process shown in FIG. 9 will be described withreference to FIGS. 10 and 11.

The flow shown in FIG. 10 is substituted for Steps S 8 to S 14 in theflow of FIG. 9, while the flow shown in FIG. 11 is usable in place ofSteps S 21 to S 26 in the flow of FIG. 5. Thus, the same Step Nos. areused in FIGS. 10 and 11 to indicate the same Steps as those in FIGS. 5and 9, respectively.

Referring to FIG. 10, the proces proceeds from Step S 9 to Step S 61which judges whether the electronic flash device 10 is to be used ornot, as in Step S 10 explained before. If the answer is NO. the processproceeds to Step S 67 to reset a flag and then to Step S 2 of FIG. 2.Conversely, when the answer is YES, charging of the main capacitor 101of the electronic flash device 10 is commenced in Step S 62 and theprocess proceeds to Step S 63 which judges whether the presentphotographing conditions may cause red-eye effect, as in the case ofStep S 12 explained before. If the answer is NO, the process proceeds toStep S 66 in which a flag FLAG 1 indicative of the use of the electronicflash device 10 alone is set. The process then proceeds to Step S 2 ofFIG. 2. Conversely, if the answer to the question posed in Step S 63 isYES, charging of the capacitor 111 of the pre-light-emission device 11is started in Step S 64 and, in Step S 65, a flag FLAG 2 indicative ofthe use of both the pre-light-emission device 11 and the electoronicflash device 10 is set. The process then proceeds to Step S 2.

Thus, in this modification, Step S 1 of the flow shown in FIG. 2 isexecuted in response to turning on of the first switch SW1. Thereafter,Steps S 2-S 9 to Steps S 61-S 67 of FIGS. 2 and 10 are repeatedlyexecuted until the second switch SW 2 is turned on.

The flow shown in FIG. 11 is interrupted when the second switch SW2 isturned on. The interrupt routine is commenced with Step S 71 judgingwhether FLAG 1 has been set. If not, the process proceeds to Step S 72.Conversely, if an affirmative answer is obtained, the process proceedsto Step S 73 in which whether the capacitor 111 of thepre-light-emission device 11 has been charged is judged. If the answeris YES, the process proceeds to Step S 74 in which a judgment isexecuted as to whether the main capacitor 101 of the electronic flashdevice 10 has been charged. If the answer is YES, Steps S 22 to S 26 areexecuted in the same manner as in the flow shown in FIG. 5 and then theprocess proceeds to Steps S 34 and S 35 of FIG. 7. If an affirmativeanswer is given to the question posed in Step S 71, the process proceedsto Step S 74. Negative answers in Steps S 73 and S 74 causes the processto proceed to Step S 75 in which a release lock is put into effect so asto inhibit the exposure. The process then returns.

Thus, in this modification, the release lock is put into effect so as toinhibit the pre-light-emission and the exposure when either one of thecapacitors 111 and 101 has not been sufficiently charged up underphotographing conditions which necessitate the use of both thepre-light-emission device 11 and the electronic flash device 10.

The release lock is put into effect also in photographing conditionswhich necessitate the electronic flash device 10 alone, whenever themain capacitor 101 has not been charged up.

The described embodiment may be modified such that a warning deviceoperates in response to a red-eye effect prevention instruction so as toinform that the photographing conditions may cause red-eye effect andthen the user inputs a pre-light-emission instruction from a separateswitch so as to activate the pre-light-emission device on condition thatboth the main flashing instruction and the charge-up signals areavailable. In such a modification, the warning device may be omitted sothat only the separate switch for inputting the pre-light-emissioninstruction is added to the described embodiment.

In the described embodiment, the photographing conditions are judged aspossibly causing red-eye effect when both the condition of the objectbrightness B being below a predetermined reference level and the objectdistance D being greater than a predetermined value are met. Under acomparatively bright condition such as at twilight time, the red-eyeeffect is not liable to occur even when the object brightness is belowthe predetermined reference level. The red-eye effect is more liable tooccur in the darkness. Taking this fact into consideration, thedescribed embodiment may be modified such that the threshold orreference object distance is set to be comparatively large andcomparatively small, respectively, when the photographing condition iscomparatively bright and dark, when the object brightness is below thepredetermined reference level.

A description will be given of an arrangement which is capable ofinforming the person to be photographed that a main flashing for theexposure is conducted following a pre-light-emission for preventing thered-eye effect, with specific reference to FIG. 12.

The flow shown in FIG. 12 can be used in place of the Steps S 21 to S 26of the flow shown in FIG. 5.

As the second switch SW2 is turned on, the interrupt routine shown inFIGS. 12, 6 and 7 is started. If an answer YES is given to the questionposed in Step S 71, a voice generating signal is given to the voicegenerating circuit 14 so that the speaker 15 generates voice to informthe person to be photographed that a pre-light-emission for the purposeof prevention of red-eye effect is going to be performed. Then, theprocess proceeds to Step S 22 in which a discharge start instruction 115is produced to activate the xenon tube XE2 thereby applyingpre-light-emission light to the person to be photographed. Inconsequence, the pupils of the person's eyes gazing at the flashinglight contract.

Then, in Step S 82, a lighting signal is delivered to the camera controlcircuit 5 so that the process proceeds to Step S 23. This step judgeswhether a predetermined time, e.g., 0.75 second, necessary for the pupildiameter to be minimized, has elapsed after the flashing of the xenontube XE2. If the answer is YES, the process proceeds to Step S 83 inwhich a display stop signal is given to the camera control circuit 5thereby turning the LED 13 off. Then, the same steps are followed asthose explained before.

This process ensures that the person to be photographed gazes at thecamera without fail when pre-light-emission for preventing occurrence ofred-eye is performed, by virtue of the voice message which inform theperson of the fact that the pre-light-emission is going to be executed.

Furthermore, since the LED 13 on the front side of the camera lights upbetween the flashings of the xenon tube XE2 and the xenon tube XE1, theperson to be photographed can correctly understand that the exposure hasnot been completed when the xenon lamp XE2 has flashed but is conductedonly at the time of flashing of the xenon tube XE1, so that the personcontinues to gaze at the camera without fail after thepre-light-emission, until the main flashing of the xenon tube XE1 isover.

The warning by the LED 13 effected in Step S 82 may be replaced by voicewarning. Either one or both of voice warning and lighting of an LED maybe used in each of Steps S 81 and S 82. Obviously, warning by voice maybe replaced with a buzzer type warning means.

In an alternative arrangement shown in FIG. 13, when the red-eye effectprevention mode is confirmed in Step S 21 of the release interruptionroutine, the process proceeds to Step S 91 in which the warning by meansof a voice, warning sound or flickering of an LED is started and, afterexecution of Steps S 22 to S 34 to complete the exposure, the warningceases in Step S 92. With this arrangement, it is possible to make theperson to be photographed gaze at the camera from the moment before thepre-light-emission for preventing red-eye effect till the completion ofthe exposure.

Preferably, an existing warning or informing device such as a self-timerinforming device is used also as the warning device such as the LED 13,voice generating circuit 14 or the speaker 15.

A description will be given of a modification in which the amount oflight emitted from the pre-light-emission device is controlled inaccordance with the object distance, such that a constant amount oflight is received by the photographing object.

FIG. 14 shows a flow chart of a process which executes the control ofthe amount of flash light emitted from the pre-light-emission device.The interrupt routine as shown in FIGS. 14, 6 and 7 is started as thesecond switch SW2 is turned on. If the camera has been set for operationin red-eye effect prevention mode in Step S 21, the process proceeds toStep S 19 in which a discharge instruction is given to the dischargecircuit 113 so that the xenon tube XE2 is activated to performpre-light-emission. Then, in Step S 92, the light quantity Q₁ on thephotographing object as detected by the photometering circuit 4 is readand, in Step S 93, a judgment is executed as to whether this lightquantity Q₁ is greater than a predetermined reference light quantity Q₀.When the detected light quantity Q₁ has reached the same level as thereference light quantity Q₀, a discharge termination instruction isgiven to the discharge circuit 113 in Step 94, whereby the discharge inthe xenon tube XE2 ceases. As a result of the pre-light-emission, thepupils of the eyes of the person to be photographed, who has gazed atthe camera, reduce their diameters.

Then, after elapse of the time required for the pupil diameter to beminimized, e.g., 0.75 second, steps of the routine shown in FIGS. 6 and7 are executed.

Thus, the flashing of the xenon tube XE2 terminates when the lightquantity Q₁ of the light applied to the photographing object isincreased to the level of the predetermined reference light quantity Q₀,so that the quantity of the pre-light-emission light received by theobject is maintained substantially constant regardless of the objectdistance. The reference value Q₀ of the light quantity is selected so asto bring about a satisfactory red-eye effect prevention without dazzlingthe person to be photographed. Therefore, the person to be photographedis relieved from dazzle which may otherwise be caused by an excessivelylarge quantity of the pre-light-emission light, even when the objectdistance is small. In addition, sufficiently large quantity ofpre-light-emission light received by the photographing object is ensuredeven when the object distance is large, thus ensuring prevention ofred-eye effect which may otherwise be caused due to shortage of thepre-light-emission light.

The arrangement may be such that a pre-light-emission deviceincorporating a pair of discharge tubes is used in place of thepre-light-emission device shown in FIG. 1, the tubes being operativesuch that one of the discharge tubes operates when the object distanceis small and both discharge tubes operate when the object distance islarge.

More specifically, a pre-light-emission device 21 shown in FIG. 15includes a pair of xenon tubes XE21 and XE22, a pair of capacitors 211aand 211b for storing electric charges to be discharged in the respectivexenon tubes, and a charging circuit 212 and a discharge circuit 213similar to those used in the described embodiment. The charging circuit212 is capable of charging both capacitors in accordance with aninstruction given by the CPU, while the discharge circuit 213 allows thexenon tubes XE21 and XE22 to fully discharge in accordance with theamount of the charges stored in the capacitors.

In this case, a region which is farther than the reference objectdistance D_(o) is divided into two regions: namely, a farther region anda nearer region. If the object is recognized to be in the fartherregion, the CPU delivers to the discharging circuit 213 a dischargeinstruction 215 for activating both xenon tubes. Conversely, when thephotographing object is in the nearer region, the CPU delivers to thedischarge circuit a discharge instruction 215 which enables only one oftwo xenon tubes to flash. Other portions are materially the same asthose in the arrangement shown in FIG. 1, so that detailed descriptionis omitted in regard to these portions.

A process performed by the CPU for effecting such a control of two xenonlamps according to the object distance will be explained With referenceto a flow chart shown in FIG. 16 in which the same reference numeralsare used to denote the same steps as those in FIG. 5.

When setting of the camera for operation in the red-eye effectprevention mode is confirmed in Step S 21 in the release interruptroutine, the process proceeds to Step S 101 in which a judgment isexecuted as to whether the object distance D ranges in the fartherregion or the nearer region. If the object is in the nearer region, theprocess proceeds to Step S 102 in which a discharge instruction is givento enable the xenon tube XE21 to flash and then the process proceeds toStep S 23. Conversely, when the object is in the farther region, theprocess proceeds to Step S 103 in which a discharge instruction is givenso as to activate both the xenon tubes XE21 and XE22. The process thenproceeds to Step S 23.

Obviously, three or more xenon tubes may be used though an examplehaving two xenon tubes has been described. In such a case, the regionbeyond the reference object distance Do is divided into a plurality ofregions and the number of the xenon tubes taking part in thepre-light-emission is increased in correspondence with an increase inthe object distance.

Although the described embodiments incorporate flash-typepre-light-emission device, the pre-light emission may be performed by anordinary lamp. In such a case, the intensity of the light from the lampis changed by varying the voltage applied to the lamp suitably inaccordance with the object distance. When a single pre-light-emissiontube is used, the arrangement may be such that the frequency of thepre-light-emission tube is changed in accordance with the objectdistance so as to provide a substantially constant light quantity of thepre-light-emission light.

In the described embodiments, the brightness of the object as measuredby the exposure control photometering circuit is used as one of theconditions for judging the possibility of occurrence of red-eye effect.This, however, is not exclusive and the arrangement may be such that aphotometering circuit capable of metering the brightness on the rearside of the camera is used in place of the exposure controlphotometering circuit. This is because the red-eye effect may not beproduced provided that the sight on the rear side of the camera which isviewed by the person to be photographed is bright, even when thebrightness of the photographing object is judged as possibly causing thered-eye effect.

A modification will be described with reference to FIGS. 17 and 18 inwhich the pre-light-emission is repeatedly conducted at a predeterminedtime interval in response to the pressing of the release button to thebottom of the first stroke so as to keep the pupils of the eyes of theperson to be photographed in such a contracted state as to preventoccurrence of the red-eye effect.

In Step S 13, the red-eye effect prevention mode is set as is in thecase of the process shown in FIG. 3. The process then proceeds to Step S111 and then to Step S 112 in which a discharge instruction is given tothe pre-light-emission device 11 so as to cause the xenon tube XE2 toilluminate over a predetermined period. The process then returns to StepS 2 and subsequent Steps are followed as explained before. This routineis repeated so that the pre-light-emission for preventing the red-eyeeffect is repeatedly executed at a predetermined time interval T untilthe switch SW2 is turned on as a result of completion of the secondstroke of the release button or until the switch SW1 is turned OFF as aresult of dismissal of pressing of the release button.

As the second switch SW2 is turned on, the interrupt routine shown inFIGS. 18, 6 and 7 is started. If the camera has been set for operationin the red-eye effect prevention mode, the process proceeds to Step S121 in which the number N of repetitions of the pre-light-emission isdetermined. If the number is 1 (one), the process proceeds to Step S 23,whereas, if the number is 2 (two) or greater, the process proceeds toStep S 24 skipping over Step S 23, so that the flashing operation isexecuted without delay.

FIG. 19 shows how the pupil size is changed in relation to time inresponse to repeated pre-light-emission. The pupil size decreases inresponse to a first pre-light-emission but tends to increase again.However, if the second and third pre-light-emissions are effected beforethe pupil size increases to such a degree as to allow red-eye effect tooccur, the pupil size further decreases as a result of these successivepre-light-emissions. In consequence, the pupil is maintained at such asmall size as not to allow the occurrence of red-eye effect.

The pupil size gets smaller as the brightness of the environmentincreases and the time required for the pupil to become large to adegree which allows the occurrence of red-eye effect increasescorrespondingly. The time interval T, therefore, is preferablycontrolled in accordance with the brightness of the object. Such acontrol eliminates any unnecessary pre-light-emission and suppresseswasteful use of the electric power.

A description will be given hereinafter of an embodiment which employs aspecific control of pre-light-emission during successive continuousflash-assisted shots.

If a predetermined time has passed after the immediately precedingflashing of the main flash device, the pre-light-emission for preventingred-eye effect is executed in advance of operation of the main flashdevice. However, if the predetermined time has not passed, the pupils ofthe person to be photographed are maintained small enough to preventoccurrence of red-eye effect as a result of flashing in the immediatelypreceding flash-assisted shot, so that the main flash device operateswithout being preceded by a pre-light-emission.

In case of a flash-assisted exposure, the CPU operates to effectpre-light-emission in response to manipulation of the second switch SW2and, when 0.75 second has elapsed thereafter, effects a shutter releaseoperation accompanied by main flashing of the electronic flash device.Time measurement is started simultaneously with a main flashing and,when the next flash-assisted exposure is to be conducted before theexpiration of a predetermined time which is, for example, 1.3 second,the operation of the pre-light-emission device is prohibited and thenext exposure with the assist of the main flash is performed withoutdelay in response to pressing of the second switch SW2. Thepredetermined time is typically a time over which the pupils' size ismaintained so small as not to allow occurrence of red-eye effect.

Referring to FIG. 20, when the red-eye effect prevention mode isconfirmed in Step S 21, the process proceeds to Step S 131 in which ajudgment is executed as to whether 1.3 second has elapsed after the mainexposure of the immediately preceding flash-assisted exposure. If theanswer is YES, the process proceeds to Step S 22 in which the xenon tubeXE2 of the pre-light-emission device 11 is activated to perform apre-light-emission and, after elapse of a time necessary to cause thepupil to contract, e.g., 0.75 second, an exposure routine beginning withStep S 24 is executed, Conversely, if the answer is NO in Step 131,i.e., when the predetermined time has not elapsed yet, the processproceeds to Step S 24 without activating the pre-light-emission device11. The measurement of the predetermined time, i.e., 1.3 second, iscommenced immediately after execution of Step S 29.

Another example of repeated pre-light-emission will be describedhereinunder.

FIG. 21 shows the manners in which the pupil size decreases in relationto time, when the pre-light-emission device 11 flashes twice with a timeinterval of 0.4 second and when the same-flashes only once,respectively.

As will be seen from the dot-and-dash line, when the pre-light-emissionis executed only once, the rate of reduction in the pupil size isdrastically increased when 0.3 second has elapsed after the emission butis decreased when 0.45 second has elapsed after the emission. The pupilsize is decreased to D_(P1) which is small enough to prevent red-eyeeffect when 0.7 second has passed after the emission.

In contrast, when the second pre-light-emission is effected, when 0.4second has passed after the first emission, rapid contraction of thepupil is continued even after elapse of 0.45 second and the pupildiameter D_(P1) is reached when 0.5 second has passed. At a moment whichis 0.7 second after the first emission, the pupil size is furtherdecreased to D_(P2) with which the occurrence of red-eye effect isfurther suppressed.

In this case, the flash-assisted exposure is conducted at a moment whichis 0.5 second after the first pre-light-emission and 0.1 second afterthe second pre-light-emission, at which the pupil diameter has beenreduced to D_(P1). However, when a higher suppression of red-eye effectis desired, the flash-assisted exposure may be conducted at a momentwhich is 0.7 second after the first pre-light-emission, in order toattain a higher effect of preventing red-eye effect.

Thus, the second pre-light-emission provides a longer period of rapidcontraction of the pupils. In consequence, the time required for thepupil to contract to a predetermined size is shortened, and a smallerpupil size is obtained at a given moment than in the case where thepre-light-emission is performed only once.

The second pre-light-emission is preferably conducted while the pupilsize is contracting comparatively rapidly, i.e., in a period which is0.3 to 0.5 second after the first pre-light-emission, as in thedescribed case, because the second pre-light-emission conducted at sucha timing ensures that the rapid contraction of the pupil is maintainedto shorten the time which is required for the pupil to contract to apredetermined small size after the first pre-light-emission.

An experiment showed that the energy to be consumed for attaining asufficiently large effect of prevention of red-eye effect is smaller inthe case where first and second pre-light-emissions are executed as inthe described case than in the case where the pre-light-emission iseffected only once.

More specifically, while the flash guide number for preventing red-eyeeffect by a single pre-light-emission was 2.8, the guide number wasabout 2.54 in the case where first and second pre-light-emissions wereconducted. The guide number in the latter case is a composite guidenumber determined as a square mean of the guide numbers in the first andsecond pre-light-emissions. It was also confirmed that the effect forpreventing red-eye effect was almost the same even if the guide numbersin the first and second pre-light-emissions are varied in variousmanners, provided that the composite guide number as the square mean isunchanged. For instance, a substantially equal prevention effect wasobtained both in a first case in which the guide numbers were equallyset at 1.8 for the first and second pre-light-emissions and a secondcase in which the guide number in the.first pre-light-emission was setat a greater value of 2.08 while the guide number for the secondpre-light-emission was set at a smaller value of 1.47. It was alsoconfirmed that the effect is substantially the same even if the firstand the second pre-light-emissions were conducted with smaller andgreater guide numbers.

When greater and smaller guide numbers are used in the first and secondpre-light-emissions, respectively, the time required for the charging ofthe capacitor to a level which enables the second light emission isadvantageously shortened.

Conversely, when smaller and greater guide numbers are used for thefirst and second pre-light-emissions, respectively, the difference inthe stimulus between these light emissions is reduced so that thefollowing advantages are brought about.

The pupil diameter is usually large when the first pre-light-emission isexecuted. Therefore, if the first pre-light-emission is conducted with alarge guide number, the eyes of the person to be photographed areexcessively stimulated imparting an unpleasant feeling. Such a problemcan be avoided by employing a smaller guide number in the firstpre-light-emission so as to reduce the stimulus.

The pupil size has been appreciably reduced when the secondpre-light-emission is executed. Therefore, the effect to reduce thepupil size produced by the second pre-light-emission is weakened. Thisproblem, however, can be overcome by applying a greater guide number tothe second pre-light-emission than to the first pre-light-emission.

In some cases, the eyes of the person to be photographed may avert fromthe camera when the first pre-light-emission is performed. However, evenin such a case, the second pre-light-emission can produce an appreciablepreventing of red-eye effect when the second pre-light-emission isexecuted with a large guide number. In such a case, the time intervalfrom the second pre-light-emission to the flash-assisted exposure isdetermined to be comparatively long, e.g., 0.4 to 0.7 second, so as toensure a sufficient contraction of the pupil caused by the secondpre-light-emission alone.

The process of this control will be explained in connection with FIG.22.

When the red-eye effect prevention mode is confirmed in Step S 21, theprocess proceeds to Step S 141 in which the voice generating circuit 14is activated to announce that a pre-light-emission for preventingoccurrence of red-eye-effect is going to be performed. The process thenproceeds to Step S 142 in which a light-emission instruction is given tothe pre-light-emission device 11 thereby conducting a firstpre-light-emission, so that the pupils of eyes of the person to bephotographed are made to contract.

In Step S 143, whether 0.4 second has passed after thepre-light-emission is judged and a second pre-light-emission isperformed in Step S 144. The second pre-light-emission ensures that thepupils contract without fail even if they failed to contract in thefirst pre-light-emission. Then, after judging whether 0.1 second haspassed in Step S 145, the process proceeds to the next step.

A second embodiment of the invention will be described with reference toFIGS. 23 to 25.

Referring to FIG. 23 which shows the general arrangement of the secondembodiment, components 1 to 6 and 8 on the camera 30, as well asswitches SW1 to SW3, are substantially the same as those shown in FIG.1.

The camera 30 has an electronic flash device 40 which is detachablysecured thereto. The electronic flash device 40 has a xenon tube XE4 anda discharge circuit 401. The discharge circuit 401 is automaticallyconnected to a CPU through a line L1 via a connection terminal 41, uponmounting of the electronic flash device 40 on the camera 30. At the sametime, the photometering circuit 4 and the camera control circuit 5 areconnected to the discharge circuit 401 through lines L2 and L3 viaconnection terminals 42 and 43.

In the case of a flash-assisted exposure which employs the electronicflash device 40, the exposure control device 5 drives the exposurecontrol device 6 in response to turning on of the second switch SW2 anddelivers a discharge start signal of a low level to the line L3. Thissignal is input to the base of the transistor Tr1 through an internalresistance R3 of the electronic flash device 40 thereby turning thetransistor Tr1 on. As the transistor Tr1 is turned on, a potential ofthe input terminal 402 of the discharge circuit 401 is set high, so thatthe discharge circuit operates to allow the xenon tube XE4 to flash andilluminate the photographing object, i.e., a main light emission isstarted.

The photometering circuit 4 has a light-receiving element which receiveslight reflected by the photographing object and determines thebrightness of the object. The thus determined object brightness isdelivered to the CPU. When the brightness of the object illuminated bythe main-light-emission reaches a predetermined level, the CPU deliversa discharge termination signal of low level to the line L2 through thephotometering circuit 4. Consequently, the input terminal of thedischarge circuit 401 is set low, whereby the xenon tube XE4 of theelectronic flash device stops illuminating.

When the flash-assisted exposure is performed, a pre-light-emissionsignal of a low level is delivered to the line L1 in response to theturning on of the second switch SW2, in advance of the main flashing.This signal is delivered to the base of the transistor Tr2 through aresistor R2 so that the transistor Tr2 is turned on, whereby the inputterminal of 402 the discharge circuit 401 is connected to the powersupply through a diode D1 so as to be set high. As a result, thedischarge circuit operates to allow the xenon tube XE4 to discharge,thereby commencing a pre-light-emission. The turning on of thetransistor Tr2 causes the capacitor C1 to be charged through theresistor R1. When a predetermined amount of charge has been reached inthe capacitor C1, i.e., when a predetermined time has passes after theturning on of the transistor Tr2, the transistor Tr3 is turned on, sothat the input terminal 403 of the light-emitting circuit 401 is set lowthereby causing the discharge circuit 401 to terminate the discharge inthe xenon tube XE4, whereby the pre-light-emission ceases.

The photometering circuit 4 receives light reflected by thephotographing object and computes the object brightness on the basis ofthe detection signal and delivers the thus determined brightness to theCPU. Upon receipt of the data concerning the object brightness obtainedas a result of the pre-light-emission, the CPU again determines theaperture value. The amount of the pre-light-emission light reaching theobject decreases as the object distance is increased, so that thebrightness of the object becomes correspondingly low. To compensate forthis reduction in the brightness, the aperture value i.e. the stop valueis increased to ensure optimum exposure at the time of flash-assistedexposure.

The CPU also judges whether the present photographing conditions maycause occurrence of red-eye effect when the flash-assisted exposure isperformed, on the basis of the object brightness. If red-eye effect isjudged as possibly occurring, the CPU sets the camera for operation inthe red-eye effect prevention mode, and controls the time interval ordelay time between the pre-light-emission and the main flashing of thexenon tube XE4, on the basis of the brightness information obtained inresponse to the pressing of the release button to the bottom of thefirst stroke. In this embodiment, the object brightness is classifiedinto three classes: namely, low brightness, medium brightness and highbrightness regions. When the object brightness as measured by thephotometering circuit belongs to the low brightness region, the delaytime is set to T₁. Similarly, the delay time is set to T₂ and T₃,respectively, when the measured object brightness belongs to medium andhigh brightness regions. The delay times T₁, T₂ and T₃ are determined tomeet the following condition:

    T.sub.1 >T.sub.2 >T.sub.3

Thus, the delay time is prolonged as the object brightness becomeslower. This is attributable to the fact that, since the pupils havecontracted to a certain degree when the object brightness is high, thetime required for the pupils to contract to a size which can preventoccurrence of red-eye effect is short as compared with the case wherethe object brightness is low.

The described process performed by the CPU will be described on thebasis of the flow chart shown in FIGS. 24 and 25.

As the first witch SW1 is turned on, an interrupt terminal of the CPU 1is set low so that the interrupt program of FIG. 24 is started. Thisprogram begins with Step S 201 in which initial resetting is performed.Namely, the memory and other components in the CPU are reset andelectrical power is supplied to the electrical circuits.

In Step S 202, a judgment is executed as to whether the first switch SW1has been turned on. If the answer is NO, the supply of power to theelectric circuits ceases and the process is finished. However, if theanswer is YES, the process proceeds to Step S 203 in which the objectbrightness and the object distance are read from the photometeringcircuit 4 and the range finding circuit 3. Then, in Step S 204, theaperture value and the time value are determined on the basis of theobject brightness and, in Step S 205, the amount of driving of the lensfor bringing the lens to the best focus position is determined. Theprocess then proceeds to Step S 206. The thus determined time value andthe lens driving amount are stored in a memory.

In Step S 206, a judgment is executed as to whether exposure to beconducted is flash-assisted exposure which

employs an electronic flash device 40. This is accomplished by judgingwhether the flash inhibition switch (not shown) has been turned on orwhether the object brightness read in Step S 203 is lower than apredetermined reference value. When the answer is NO in Step S 206, theprocess proceeds to Step S 209 in which the red-eye effect preventionmode is dismissed and then the process returns to Step S 202.Conversely, if the answer is YES, a judgment is executed as to whetherthe photographing conditions may cause red-eye effect. Thus, the CPUjudges that the red-eye effect may when the object brightness read inStep S 207 is higher than a predetermined threshold value for thegeneration of red-eye effect, and that the red-eye effect will not occurwhen the object brightness is below this threshold.

If the answer to the question posed in Step S 207 is NO, the red-eyeeffet prevention mode is dismissed in Step S 209. Conversely, if theanswer is YES, the camera is set for operation in the red-eye effectprevention mode in Step S 208. The process then returns to Step S 202and the described operation is repeated.

When the second switch SW2 is turned on in this state, the interruptprogram shown in FIG. 25 is started. In Step S 221, judgment is executedas to whether the photographing operation to be conducted is theflash-assisted exposure which requires the use of the electronic flashdevice 40. If the answer is YES, the process proceeds to Step S 222 and,if the answer is NO, the process proceeds to Step S 233. In Step S 222,a pre-light-emission start signal is delivered to the line L1 therebyeffecting the pre-light-emission. As a result, the transistor Tr2 isturned on so that the input terminal 402 of discharge circuit 401 is sethigh, so that the discharge circuit 401 activates the xenon tube XE4thereby allowing the same to emit light.

The turning on of the transistor Tr2 initiates the charging of thecapacitor C1 and, when the amount of charge in this capacitor hasreached a predetermined value, the transistor Tr3 is turned on to setthe input terminal 403 of the discharge circuit 401 low, whereby thedischarge circuit 401 operates to terminate the discharge in the xenontube XE4.

The process then proceeds to Step S 223 in which the quantity of thepre-light-emission light reflected by the object, i.e., the objectbrightness, is read from the photometering circuit 4. Then, the CPUcomputes the aperture value on the basis of the object brightness, andproceeds to process to Step S 225 which determines whether the camerahas been set for operation in the red-eye effect prevention mode. If theanswer is NO, the process proceeds to Step S 230, whereas, if the answeris YES, the process proceeds to Step S 226. Step S 226 determineswhether the object brightness as read in Step S 223 belongs to the highbrightness region BH, medium brightness region BM or the low brightnessregion BL. When the measured object brightness is judged to belong tothe high brightness region BH, the process proceeds to Step S 330 afterelapse of the delay time T₃ in Step S 230. Similarly, the processproceeds to Step S 230 after elapse of the delay times T₂ and T₁,respectively, when the measured brightness belongs to the medium and lowbrightness regions BM and BL, respectively.

In Step S 230, the focusing lens driven to the best focus position inaccordance with the lens driving amount which is determined in Step S205. The process then proceeds to Step S 231 in which an operationsignal is delivered to the camera control circuit 5, thereby performingflash-assisted exposure.

In response to the operation signal, the camera control circuit 5operates the exposure control device 6 in accordance with the time valuedetermined in Step S 205 and the aperture value determined in Step S224, while delivering a discharge start signal to the line L3. Inconsequence, the transistor Tr3 is turned on so that the input terminal402 of the discharge circuit 401 is set high, so that the dischargecircuit 401 activates the xenon tube XE4 thereby effecting mainflashing. In Step S 231, an operation also is conducted for reading thebrightness of the object illuminated by the main flash and, when thisbrightness has reached a predetermined value, the CPU delivers adischarge termination signal thereby to terminate the emission of lightfrom the xenon tube XE4.

If the answer to the question posed in Step S 221 is NO, the focusinglens 8 is moved to the best focus position in Step S 232 and, in Step S233, the camera control circuit 5 drives the exposure control device 6in accordance with the aperture value and the time value determined inStep S 204, whereby the exposure is executed in the ordinary mode.

Thus, in this embodiment, the first pre-light-emission is executed whenthe release button is pressed to the bottom of the second stroke in theflash-assisted exposure mode and, when the instant photographingcondition is judged as possibly causing red-eye effect, the shutterreleasing operation accompanied by the main flashing is executed afterelapse of the delay time. Thus, the pre-light-emission enables both thedetermination of the aperture value and the prevention of the red-eyeeffect, so that there is no need for execution of repeatedpre-light-emission, whereby wasteful use of the battery power, as wellas confusion of the person to be photographed, is avoided. When theinstant photographing condition is judged as not possibly causingred-eye effect, the exposure under the main flash is executed withoutfail so that unintentional delay in the shutter release operation can beavoided.

In the described embodiment, the delay time can be varied in threestages. This, however, is not exclusive and the delay may be effected intwo stages or in four or more stages. Furthermore, it is possible totake into account the object distance in addition to the objectbrightness, as the factor for determining the possibility of occurrenceof red-eye effect. In general, red-eye effect becomes more liable tooccur when the angle between the line interconnecting the photographingobject and the exposure lens and the line interconnecting thelight-emission portion of the electronic flash device and thephotographing object is below a predetermined angle which is, forexample, about 2.5°. Thus, the second embodiment may be modified so thatthe photographing conditions are judged as possibly causing red-eyeeffect when the object distance is-greater than a value whichcorresponds to the above-mentioned angle while the object brightness isbelow a predetermined level.

A description will be given of a third embodiment of the presentinvention which is designed such that the pre-light-emission forpreventing occurrence of red-eye effect is performed without delaywhenever the exposure is conducted in a timer-assisted exposure mode.

Referring to FIG. 26 showing the general arrangement of the thirdembodiment, a focus detection circuit 3, a photometering circuit 4, acamera control circuit 5, a lens drive circuit 2 and first and secondswitches SW1, SW2 are connected to a CPU 1. An exposure control device 6for controlling the exposure conditions such as the time value and theaperture value is connected to the camera control circuit 5. As in thecases of the preceding embodiments, the first and second switches SW1and SW2 are turned on in relation to a manipulation of a release button.In response to turning on of the switch SW1, the CPU 1 activates thefocus detection circuit 3 and the photometering circuit 4 and, inresponse to turning on of the switch SW2, activates the motor drivingcircuit 2 and the camera control circuit 5.

An electronic flash device 50 serving also as a pre-light-emissiondevice for preventing occurrence of red-eye effect, a timer circuit 51and switches SW3 to SW5 are connected to the CPU. The electronic flashdevice 50 includes a light emission tube XE5, main capacitors 501, 502for storing charges which are to be discharged in the light emissiontube XE5, a charging circuit 503 for charging these capacitors, and adischarge circuit 504 for controlling the timing of start of thedischarging of the light emission tube XE5. The main capacitor 501stores charges which are to be discharged when the light-emission tubeXE5 performs a main flashing at the time of exposure in response to ashutter releasing operation. On the other hand, a sub-capacitor 502stores charges which are to be used in a pre-light-emission from thelight-emission tube XE5 in advance of the main flashing for the purposeof preventing occurrence of red-eye effect. The charging circuit 503 iscapable of charging main and sub-capacitors in response to aninstruction given by the CPU and produces a charge-up signal upondetection of completion of charging of each capacitor. The dischargecircuit 504 causes the light-emission tube XE5 to perform main flashingin response to a main flashing start signal given by the CPU, andterminates the main flashing in response to a main flashing terminationsignal delivered by the CPU. The discharge circuit 504 also starts andterminates the pre-light-emission in response to a pre-light-emissionstart signal and a pre-light-emission termination signal, respectively.

The switch SW3 is a momentary-type-switch which operates in relation topressing of a flash change-over switch (not shown). Successive turn-onoperations of the switch SW3 cause the CPU to successively set thecamera operation mode from an automatic-flashing mode to a compulsoryflashing mode and then to a flash prohibition mode. The automaticflashing mode is a mode in which whether the main flashing is to beexecuted is determined on the basis of the brightness informationdelivered by the photometering circuit 4. According to this mode,therefore, the exposure is performed in flash-assisted mode when theobject brightness is low. The compulsory flashing mode is a mode inwhich the main flashing is executed at the time of exposure regardlessof the level of the object brightness. The flash prohibition mode is amode in which the exposure is executed without the assist of the flashdevice even when the object brightness is low. Thus, the main flashingis required when the compulsory flashing mode has been selected or whenthe object brightness is low in the automatic flashing mode. In such acase, the main capacitor 501 is charged to enable the flash-assistedexposure. A light-emission signal (main flashing instruction) is givento the discharge circuit 504 simultaneously with the shutter release sothat the main flashing is performed with the charged stored in the maincapacitor 501.

The switch SW4 is operatively associated with a push button (not shown)which is pressed when the red-eye effect is to be prevented. A red-eyeeffect prevention mode setting signal is produced as the switch SW4 isturned on. In response to this signal, the CPU sets the camera foroperation in the red-eye effect prevention mode and allows thesub-capacitor 502 to be charged through the charging circuit 503. Then,the red-eye effect prevention instruction is given to the light-emissioncircuit in response to turning on of the second switch SW2, so that thelight-emission tube XE5 flashes with the charges from the sub-capacitor502 in advance of the main flashing which is to be executed in responseto the shutter releasing operation, whereby the pre-light-emission isperformed. The red-eye effect prevention mode is dismissed when theswitch SW4 is turned off, so that the above-mentioned pre-light-emissionis not conducted.

The switch SW5 is adapted to be turned on in relation to the operationof a self-timer button which is not shown. A self-timer mode settingsignal is produced when the switch SW5 is turned on. In response to theself-timer mode setting signal, the CPU sets the camera for operation inthe self-timer mode and, in response to turning on of the second switchSW2, delivers a timer instruction to the timer circuit 51 therebyenabling the timer circuit to count the time. After the predeterminedtime has elapsed, the CPU allows the shutter to be released, wherebyexposure is conducted.

When the above-described conditions for the flash-assisted exposure aresatisfied after the camera is set in the self-timer mode, the CPUdelivers the red-eye prevention mode setting signal to the dischargecircuit 504 regardless of the state of the red-eye effect preventionswitch SW4.

The operation of this embodiment will be explained in connection withFIG. 27 which shows a flow chart illustrating the operation.

As the first switch SW1 is turned on, the CPU reads distance data andbrightness data and determines the amount of driving of the lens, aswell as the exposure value.

In Step S 301, the CPU judges the type of the flash-assisted exposuremode. If the instant mode is the automatic flashing mode (MODE A), ajudgment is executed in Step S 302 as to whether the main flashing ofthe light-emission tube XE5 is to be executed or not, on the basis ofthe brightness information. This judgment is executed by judging whetherthe level of the brightness information B is less than a predeterminedlevel B₀. When the level of the brightness information is low so thatthe main illumination is necessary, an answer YES is given in responseto the question posed in Step S 302. Conversely, an answer NO is givenwhen the level of the brightness information is higher than thepredetermined level, i.e., when the main flashing is not needed. Whenthe compulsory flashing mode (MODE C) has been selected, the processproceeds to Step S 303 and, when the flashing prohibition mode (MODE P)has been selected, the process proceeds to Step S 307.

An answer NO given to the question posed in Step S 302 causes theprocess to proceed to Step S 307 in which a judgment is executed as towhether the self-timer switch SW 5 has been set on. An affirmativeanswer to this question causes the process to proceed to Step S 308 inwhich the camera is set for a self-timer mode. Conversely, when theanswer to the question posed in Step S 302 is YES, the process proceedsto Step S 303 in which a flashing flag is set and the charging of themain capacitor is commenced through the charging circuit. The processthen proceeds to Step S 304 in which whether the self-timer switch SW5has been turned on is determined. If the answer is NO, the processproceeds to Step S 309 in which a judgment is executed as to whether thered-eye effect prevention switch SW4 has been set on. If the answer tothe question posed in Step S 309 is YES, the CPU sets the camera foroperation in the red-eye effect prevention mode in Step S 306 and,whereas, if the answer is NO, the process proceeds to the next stepwithout setting the red-eye effect prevention mode.

When the answer to the question posed in Step S 304 is YES, the processproceeds to step S 305 in which the camera is set for operation in theself-timer mode. Then, the camera is set for operation in the red-eyeprevention mode in Step S 306. The process then proceeds to the nextstep.

Thereafter, as the second switch SW2 is turned on, the CPU operates todrive the focusing lens to a focusing position and conduct an exposureby suitably driving the shutter and the diaphragm. If theabove-mentioned main flashing flag has been set, a discharge startsignal is given to the discharge circuit so that the light-emission tubeXE5 flashes with the charges of the main capacitor, whereby the mainflashing is executed. If the camera has been set for operation in thered-eye effect prevention mode, a red-eye effect prevention instructionis given in response to the turning on of the second switch SW2, so thatthe pre-light-emission is performed by the light-emission tube XE5 withthe charges delivered by the sub-capacitor and, after elapse of apredetermined time, e.g., 0.75 second, the shutter is operated to causethe light-emission tube XE5 to perform the main flashing. It istherefore possible to avoid occurrence of red-eye effect.

If the flashing flag has been set while the camera has been set in theself-timer mode, a self-timer operating instruction is delivered to thetimer circuit 51 thereby starting the measurement of the time inresponse to the turning on of the second switch SW2. Since the red-eyeeffect prevention mode has been set without fail whenever theflash-assisted photographing mode is used in the self-timer mode, thelight-emission tube XE5 performs the pre-light-emission without failwhen the predetermined time is counted. Then, after elapse of apredetermined time, the shutter is released simultaneously with the mainflashing of the light-emission tube XE5.

As will be understood from the foregoing description, the camera is setfor operation in the red-eye prevention mode regardless of whether thered-eye effect prevention switch SW4 has been turned on or off, when thecamera is used in the self-timer mode under a photographing conditionwhich requires the assist of a flash. The self timer mode is used inmost cases when the photographing object includes persons so that thephotographs taken in the self-timer mode often suffer from red-eyeeffect. This means that the red-eye effect prevention operation ispreferably conducted in the flash-assisted exposure in the self-timermode. It will be seen that the present invention eliminates thenecessity for a manipulation of the red-eye effect prevention device andcan eliminate occurrence of red-eye effect which may otherwise be causedwhen the user has forgotten to set the red-eye effect prevention mode.

FIG. 28 shows examples of the red-eye effect prevention switch SW4 andthe self-timer switch SW5 which are suitable for use in this embodiment.A manipulation member 58 which slightly projects from the camera cover53 is movable in the direction of an arrow A. An arrow mark 581 is puton the manipulation member 58. Brushes 521, 522 and 523 are integrallyattached to a lower portion of the manipulation member 58.

A pattern 55 is put on the upper surface of a rigid printed board fixedin the camera in such a manner as to be always contacted by the brush521. Similarly, patterns 56 and 57 are arranged for contact with brushes522 and 523. The pattern 55 is grounded. The arrangement is such that,when the brush 522 contacts the pattern 56, the patterns 55 and 56 areelectrically connected through the brushes 521 and 522. The brushes 521,522 and the patterns 55, 56 in cooperation provide the above-mentionedred-eye effect prevention switch SW4. When the brush 523 is brought intocontact with the pattern 57, the patterns 55 and 57 are electricallyconnected to each other through the brushes 521 and 523. The brushes521, 523 and the patterns 55, 57 in cooperation provide theaforementioned self-timer switch SW5. It will be seen that the red-eyeeffect prevention switch SW4 is conductive without fail whenever theswitch SW5 is conductive.

Gradations are provided on the upper surface of the camera cover 53 atthree positions, and marks reading "OFF", "RED-EYE PREVENTION ON" and"TIMER ON" are printed near these three gradations. The contact betweenthe brushes and patterns is achieved such that a click feeling can beobtained when the manipulation member 58 has been moved to bring thearrow 581 thereon to one of these three positions.

FIGS. 29A and 29B show another example of the red-eye effect preventionswitch SW4 and the self-timer switch SW5. The red-eye effect preventionswitch SW4 and the self-timer switch SW5 are provided on the upper sideof the camera body 61 so as to slightly project therefrom asillustrated. These switches SW4 and SW5 are movable between therespective ON and OFF positions along grooves 61a and 61b, respectively.Arrows on the upper surfaces of these switches 62 and 63 represent,respectively, directions of movement of these switches.

The ON and OFF positions of these switches are displayed on the uppersurface of the camera body 61.

The camera is set for operation in the red-eye effect prevention modewhen the switch SW4 is manipulated to bring an index 62a thereon intoalignment with the ON position. Likewise, when the switch SW5 ismanipulated to bring an index 63a thereon into alignment with the ONposition, the camera is set for operation in the self-timer mode.

Thus, in the present invention, the self-timer mode cannot be attainedunless the camera has been set for operation in the red-eye preventionmode.

A fourth embodiment of the invention will De described hereinunder withreference to FIGS. 30 to 42.

This embodiment includes mean for informing the object person of thenumber of times of pre-light emission or the total number of times ofboth of pre-light emission and main light emission previous to the startof photographing. Therefore, the person whose picture is to be taken canobtain information as to the number of times of light emission.

FIG. 30 shows the construction of the embodiment. The generalconstruction shown in FIG. 30 substantially corresponds to that in FIG.1 with the exception of a display driver 70 and two light emittingdiodes (LEDs) 71, 72 connected to the signal transmission lines BL1.

The LED 71 is provided at a position on the front side of the camera (aposition which the object person can recognize). The other LED 72 isprovided within the view-finder (that is, a position which thephotographer recognize).

The display driver 70 has, as shown in FIG. 31, input terminals I₁, I₂,CLOCK and RESET, AND gates 73, 74 and 75, an OR gate 76 and flip-flopsFF1 and FF2.

The display switch signal input terminals I₁ and I₂ are connected to theinput terminals of the AND gates 73, 74 and 75 respectively. Thereference clock terminal CLOCK is connected to the input terminals ofthe AND gates 74 and 75, and to a terminal T of the flip-flop FF1respectively. A clock signal as shown in FIG. 32(d) is applied to theterminal CLOCK from CPU1. The terminal RESET is connected to the resetterminals R of the flip-flops FF1 and FF2. The terminal Q of theflip-flop FF1 is connected to the terminal T of the flip-flop FF2. Theterminals Q of the flip-flops FF1 and FF2 are connected to theirterminals D respectively.

The output terminals of the AND gates 73, 74 and 75 are connected to theinput terminals of the OR gate 76 the output of which is, in turn,connected to the base of an NPN transistor 77. The emitter of thetransistor 77 is grounded and the collector thereof is connected to apower supply through the LEDs 71, 72 and resistors 78, 79. When theoutput of the OR gate 76 is turned to High level, the transistor 77 isturned conductive (ON) and LEDs 71, 72 put on. CPU1 applies a certainsignal to the input terminals I₁ and I₂ to make LEDs 71, 72 light up orflicker in the manner which will be described later.

Further, when the switch SW1 is closed (ON) and the conditions for flashphotographing are determined, the CPU1 judges this from the computedobject distance D and object brightness B if the photographing conditionis the red eye condition (a further description thereof will be givenlater). If the judgment is for the red eye condition and the switch SW3is opened (OFF), then the CPU1 generates a signal to set the red eyeprevent mode and displays the number of light emission times by LEDs 71and 72 through the display driver 70 at the same time. In thisembodiment, the number of light emission times is "2" which is the sumof an emission from the electronic flash device 10 and an emission fromthe pre-light emission device 11.

Thereafter, with turn-ON of the switch SW2, the CPU1 applies anoperation signal to the pre-light emission device 11 to operate it.After the lapse of 0.75 seconds, the CPU1 drives the exposure controller6 through the camera control circuit 5 and, at the same time, applies anemission start signal to the electronic flash device 10.

The procedure of control by the CPU1 will be described with reference tothe flow chart shown in FIG. 33.

Upon the turn-ON of the half-stroke switch SW1, the steps S1 to S7 inFIG. 1 and S401 and S402 in FIG. 33 are perfomred in the same manner asin the first embodiment described above. At the next step S403, the CPU1checks whether the electronic flash device 10 is to be used forphotographing. When flash light photographing is denied at step S405,the procedure is advanced to step S409 where the CPU1 turns to Low levelboth of the input terminals I₁ and I₂ of the display driver 70 (FIG. 31)to make a display informing "not flash light photographing" by LEDs 71and 72. Then, the process is advanced to step S412. Thereby the outputsof AND gates 73, 74 and 75 are all turned to Low level and also theoutput of OR gate 76 is turned to Low level. The transistor 77 is,therefore, not conductive and both of LEDs 71 and 72 remain OFF. At stepS412, the red eye prevent mode is cancelled and the procedure returns tothe step S2 in FIG. 2.

If the main condenser has not been completely charged at the step S404,the terminal I₁ is turned to High level and I₂ to Low level to make adisplay at step S410 indicating that the charging is incomplete.Thereafter, the procedure is advanced to the step S412. As a result, theoutputs of AND gates 73 and 75 are turned to Low whereas the output ofAND gate 74 is intermittently turned to High by the clock signal (FIG.32(d)) inputted from the terminal CLOCK. Consequently, the output of ORgate 76 is also intermittently turned to High level. In response tothis, the transistor 77 is turned ON and OFF repeatedly and both of LEDs71 and 72 flicker.

When the condition for red dye is satisfied at step S405, the procedureis advanced to the next step S406. If not, the procedure is advanced tostep S411.

At the step S411, both of the terminals I₁ and I₂ are turned to Highlevel to make a display informing that ordinary photographing withoutred eye prevention is executed and the charging has been completed. Theprocedure is further advanced to step S412. The outputs of AND gate 73and OR gate 76 are turned to High level and the transistor 77 iscontinuously rendered conductive to put LEDs 71 and 72 on.

At the step S406, CPU1 judges whether the switch SW3 is ON or not. WhenYes, the procedure is advanced to S411. If No, then the red eye preventmode is set at the step S407. Thereafter, the number of light emissiontimes is displayed at S408. To this end, as shown in FIG. 32(b) and (c),the terminal I₁ is turned to Low level and the terminal I₂ is turned toHigh level. At the same, the terminal RESET is turned to Low level (attime point T2) and the procedure is turned back to the step S2 to repeatthe above processings.

FIG. 32 shows the change of signal level with time at every terminal. T1is a time point at which the switch SW1 is turned ON. By S408, both ofthe outputs of AND gates 73 and 74 are turned to Low level. On the otherhand, the clock signal from the terminal CLOCK is being put in theterminal T of the flip-flop FF1. The output from its terminal Q has asignal form as shown in FIG. 32(f). This output is applied to theterminal T of the flip-flop FF2 whose output at Q terminal has a signalform as shown in FIG. 32(g). The output from the terminal Q of theflip-flop FF2 and the clock signal from the terminal CLOCK are being putinto the AND gate 75. Thereby, the output of the OR gate is turned toHigh level two times during the time of from T2 to T3 as shown in FIG.32(h). During the time of T3 to T4, the output is Low level and then itis turned again to High level two times for the time of T4 to T5. Thisis repeated so long as the switch SW1 is ON. In response to the outputof the OR gate 76 the transistor 77 repeats ON-OFF. Consequently, theLEDs 71 and 72 repeat two times of ON-OFF at regular time intervals asshown in FIG. 32(i) so long as the switch SW1 is ON. This "two" times ofON-OFF indicates the number of light emission times for photographing tobe done.

By closing the switch SW2 in this state of operation, the interruptroutine (FIG. 34 and FIGS. 6 and 7) is started. The steps in FIG. 34correspond to the steps S21 to S26 in FIG. 5 with the exception of stepS420.

According to the procedure described above, LEDs 71 and 72 make adisplay to the effect that the light emission will be done twice bydepressing the release button a half stroke for flash lightphotographing with red eye prevent pre-light emission. Thus, when therelease button is fully depressed, a pre-light emission (the firstemission) is done and, 0.75 seconds after the first emission, asexposure is performed with a main light emission (the second emission).

In this manner, previous to an exposure, both of the object person andthe photographer can be informed that the light emission is to be donetwice. Therefore, the object person continues to look at the camerauntil the second emission is completed. Before the photographing isfinished, the object person will neither change his or her face noralter his or her posture.

Of the two LEDs 71 and 72, the one provided on the front side of thecamera, that is, the LED 71 may serve also as the LED for indicatingthat the self timer is counting.

A modification of the above embodiment is shown in FIGS. 35 to 38. Inthese figures, the same reference numerals and characters as those inFIGS. 31 to 34 designate the same or corresponding parts or steps whichneed not be further described. A description will be given of themodified parts only.

Referring to FIG. 35, the output terminal Q of the flip-flop FF1 isconnected to the input terminal T of the flip-flop FF2 and also to theinput terminal of the OR gate 81. Also, the output terminal Q of theflip-flop FF2 is connected to the input terminal of the OR gate 81 whoseoutput is connected to the input terminal of the AND gate 80.

In a camera according to the present modification, in order to preventthe red eye more surely for flash light photographing, the pre-lightemission previous to a main light emission is done twice. Morespecifically, the pre-light emission device 11 emits light twiceprevious to a main light emission from the electronic flash device 10.Therefore, in this modification, the total number of the emission timesincluding the main emission is "3".

At the step S406 in the flow chart shown in FIG. 37, it is checkedwhether the switch SW3 is ON or not. If it is not ON, then the red eyeprevent mode is set at step S407. Also, the number of light emissiontimes is displayed at S430. To this end, as shown in FIG. 36(b) and36(c), the terminal I₁ of the display driver 70 is turned to Low leveland the terminal I₂ is turned to High level. In the same manner as inthe above embodiment, both of the outputs of AND gates 73 and 74 areturned to Low level. The outputs from the terminals Q of the flip-flopsFF1 and FF2 also have the signal forms as shown in FIG. 36(f) and 36(g)respectively. The output from the OR gate 81 has the form as shown inFIG. 36(j). Since the clock signal from the terminal CLOCK is being putinto the AND gate 85, the output of the OR gate 76 is, as shown in FIG.36(h), turned to High level three times during the time of from T2 toT3. For the time of T3 to T4, the output is Low level and then it isturned again to High level three times for the time of T4 to T5. This isrepeated so long as the switch SW1 is ON. In response to the output ofthe OR gate 76, the transistor 77 repeats On-OFF. Consequently, the LEDs71 and 72 repeat three ON-OFFs at regular time intervals as shown inFIG. 36(i) so long as the switch SW1 is ON. This "three" times of ON-OFFindicates the number of light emission times for photographing to bedone.

By closing the switch SW2 in this state of operation, the interruptroutine shown in FIG. 38 is started.

At the first step S431, the LEDs 71 and 72 are turned OFF. At the nextstep S432, it is checked whether the red eye prevent mode has been setor not. When it is YES, the procedure is advanced to step S433 where anoperation signal is applied to the pre-light emission device 11 to flashthe xenon tube Xe2. This is a first pre-light emission. By the flashlight from the xenon tube Xe2, the pupils of the object person's eyeswill be closed.

At the step S434, it is checked whether 0.4 seconds have elapsed fromthe first pre-light emission. When it is YES, the procedure is advancedto step S435 where an operation signal is applied to the pre-lightemission device 11 to have the xenon tube Xe2 flash. This is a secondpre-light emission. Receiving the flash light from the xenon tube Xe2,the object person's pupil will surely be closed even when it has notbeen closed by the first pre-light emission. After that, the steps S437to S439 are carried out and the procedure is advanced to step S27 inFIG. 6.

According to the procedure described above, LEDs 71 and 72 make adisplay to the effect that the light emission will be done three timesby the photographer's depression of the release button to the firststroke for flash light photographing with red eye prevent pre-lightemission. Thus, when the release button is depressed to the secondstroke, two pre-light emissions are done and thereafter an exposure isperformed with a main light emission.

In this manner, previous to an exposure, the object person is informedof the fact that the light emission is to be done three times. Thus, thesame effect as described above can be obtained.

FIGS. 39 and 40 show another modification of the embodiment.

Referring to FIG. 39, the terminals I₁ and I₂ of the display driver 440are connected to the input terminals of AND gates 441, 442 and 443. Theterminal CLOCK is connected to the input terminal of the AND gate 442.The output terminals of the AND gates 441, 442 and 443 are connected tothe input terminals of the OR gate 444 respectively. Also, the outputterminal of the AND gate 443 is connected to transistors 446 and 447.The output terminal of the OR gate 444 is connected to transistor 445.The emitters of the transistors 445, 446 and 447 are grounded and theircollectors are connected to a power supply through LEDs 4481, 4482,4491, 4492, 4501 and 4502 and resistors 451. In this modification, theLEDs 4481, 4491 and 4501 are provided on the front side of the camera(at the position which the object person can recognize). LEDs 4482, 4492and 4502 are within the view-finder of the camera. In this modificationalso the pre-light emission previous to a main light emission is carriedout twice.

Steps in FIG. 40 correspond to those in FIG. 37 with the exception ofsteps S461 to S464.

In the flow chart shown in FIG. 40, when the step S403 is "NO", all ofthe LEDs are turned OFF at step S461. When the step S404 is "NO", theprocedure is advanced to step S462 where the terminal I₁ is turned toHigh level and I₂ to Low level. Thereby, the output of AND gate 442 isturned to High level and the outputs of AND gates 441 and 443 are turnedto Low level. As a result, only one transistor 445 is intermittentlyconducting. The LEDs 4481 and 4482 flicker. The remaining LEDs 4491,4492, 4501 and 4502 are all OFF. Both of the object person and thephotographer recognize that only one LED is flickering, which is asignal informing that the charging has not been completed yet.

Further, when the judgement is "NO" at step S405 or S406, the procedureis advanced to step S463 where both of the terminals I₁ and I₂ areturned to High level. As a result, only the output of AND gate 441 isturned to High level and only the transistor 445 continues to beconductive. Consequently, LEDs 4481 and 4482 are ON. Both of the objectperson and the photographer recognize that only one LED is lit, which isa signal informing that no pre-light emission is to be done and thecharging has been completed.

When it is verified that the switch SW3 is ON at the step S406, theprocedure is advanced to the step S464 through step S407. At the stepS464, the terminal I₁ is turned to Low level and the terminal I₂ isturned to High level. As a result, only the output of AND gate 443 isturned to High level, and the transistors 445, 446 and 447 are allconducting. Consequently, all of the LEDs are turned ON. Both of theobject person and the photographer recognize that three LEDs are lit on,informing that the light emission will be done three times. Thereafter,as previously described, the program shown in FIG. 38 is executed whenthe switch SW2 is closed.

Although, in the above embodiment, the number of emission times has beendisplayed by light-on of an LED, it is to be understood that the numberof emission times may be displayed also by flickering of an LED.Further, the manner of display as described above in connection with themodification shown in FIG. 39 may be replaced by a digital display usinga 7-segment LED as shown in FIGS. 41A and 41B.

In this modification, 7-segment LEDs 470 are provided, one on the frontside of the camera (at the position which the object person canrecognize) and one within the view-finder of the camera. The number oflight-emission times is displayed digitally by a numerical characterformed by the 7-segment LED 470 as illustrated by FIGS. 41A and 41B.

In this embodiment, the procedure of the process is controlled inaccordance with the flow chart shown in FIG. 42.

At the step S403, discrimination is made as to whether the photographingis to be done with flash light. When it is not, all the segments of LEDs476 are turned off at step S471 to inform that no flash lightphotographing is to be done. Further, when it is verified at step S404that the charging of the capacitor has not been completed yet, all ofthe segments are caused to flicker at step S472 to indicate theincomplete charging. When it is verified at step S405 that the red eyecondition is present or at step S406 that the switch SW3 is ON, theprocedure is advanced to the step S473 where only two segments arelighted or caused to flicker to display a character "1" as shown in FIG.41A. The displayed number "1" indicates that the number of lightemission times is one and the charging has been completed. Further, ifthe switch SW3 is not ON (step S406), the procedure is advanced to thestep S474 through step S407. At the step S474, five segments of LED arelighted or caused to flicker to display a character "3" as illustratedin FIG. 41B. The displayed numerical character "3" indicates that thenumber of light emission times is three (two pre-emissions+one mainemission).

It is to be Understood that in the fourth embodiment described above,various modifications and changes are possible. For example, althoughthe pre-emission previous to a main emission has been done twice in theabove embodiment, the number of the pre-emission times may be increasedto three or more. Further, it may be so modified that the number of thepre-light emission times is variable depending on the object distance D.In this case, the manner of display by LEDs also must be changed so thatthe real number of light emission times can be displayed.

As a further modification, acoustic means may be used for informing thenumber of emission times. For example, the speaker 15 shown in FIG. 1may be used for this purpose.

Further, although the total number of times of pre-emission and mainemission has been displayed in the above embodiment, it may be somodified to display the number of pre-emission times only.

What is claimed is:
 1. A camera comprising:a main illuminating deviceoperable to provide main illumination; a pre-illuminating deviceoperable to provide pre-illumination before main illumination; aselecting device which selects whether or not said pre-illuminatingdevice should be operated; a control device which controls operation ofsaid pre-illuminating device so as to operate said pre-illuminatingdevice when said selecting device selects that said pre-illuminatingdevice should be operated; a counter responsive to operation of saidpre-illuminating device under the control of said control device, whichstarts to count a predetermined time; and an exposing device whichexposes a film; wherein, when said selecting device selects that saidpre-illuminating device should be operated, said exposing device startsto expose said film after said pre-illumination, with a delay therefrombased on said predetermined time, and when said selecting device selectsthat said pre-illuminating device should not be operated, said exposingdevice starts to expose said film without said delay.
 2. A cameraaccording to claim 1, wherein said illuminating device emitsillumination light which reduces a red-eye effect.
 3. A camera accordingto claim 1, wherein said illuminating device is releasable from saidcamera.
 4. A camera according to claim 1, wherein said counter starts tocount substantially simultaneously with operation of said illuminatingdevice.
 5. A camera according to claim 1, wherein said counter starts tocount 0.75 second in response to operation of said illuminating device.6. A camera according to claim 1, wherein said exposing device executesat least one activation of an aperture drive, a mirror-up drive and ashutter drive.
 7. A camera according to claim 1, wherein said controldevice operates said illuminating device together with a shutter drive.8. A camera according to claim 1, wherein said control device inhibitsan operation of said pre-illuminating device when it is detected that acharge for illumination of said pre-illuminating device is notcompleted, even if said selecting device selects that saidpre-illuminating device should be operated.
 9. A camera according toclaim 1, wherein said selecting device automatically selects whether ornot said pre-illuminating device should be operated, based on at leastone of an object luminance and an object distance.
 10. A cameraaccording to claim 1, wherein said selecting device includes anoperating member manually operable by a photographer.
 11. A cameraaccording to claim 1, further comprising a first photograph commandswitch, and a second photograph command switch, which are sequentiallyturned on,wherein said selecting device selects whether or not saidpre-illuminating device should be operated, in response to said firstphotograph command switch being turned on, and when said selectingdevice selects that said pre-illuminating device should be operated,said control device operates said pre-illuminating device in response tosaid second photograph command switch being turned on.
 12. A cameraaccording to claim 11, wherein said selecting device selects inaccordance with whether a condition is established in which at least anelectronic flash device should be used.
 13. A camera according to claim11, wherein said selecting device selects in accordance with whether acondition is established in which at least a red-eye effect should becaused.
 14. An electronic flash apparatus comprising:a main illuminatingdevice operable to provide main illumination; a pre-illuminating deviceoperable to provide pre-illumination before main illumination; aselecting device which selects whether or not said pre-illuminatingdevice should be operated; a control device which controls operation ofsaid pre-illuminating device so as to operate said pre-illuminatingdevice when said selecting device selects that said pre-illuminatingdevice should be operated; a receiving circuit operable to receive astart signal to start operation of said pre-illuminating device whensaid selecting device selects that said pre-illuminating device shouldbe operated; a counter responsive to the receiving of said start signalby said receiving circuit, which starts to count a predetermined time;and an outputting device which outputs an exposure start signal whichstarts an exposure operation of a film after laid pre-illumination, witha delay therefrom in accordance with said predetermined time, when saidselecting device selects that said pre-illuminating device should beoperated, and outputs an exposure start signal which starts an exposureoperation of said film without said delay when said selecting deviceselects that said pre-illuminating device should not be operated.
 15. Anelectronic flash device according to claim 14, wherein said illuminatingdevice emits illumination light which reduces a red-eye effect.
 16. Anelectronic flash device according to claim 14, wherein said counterstarts to count substantially simultaneously with operation of saidilluminating device.
 17. An electronic flash device according to claim14, wherein said counter starts to count 0.75 second in response tooperation of said illuminating device.
 18. A method of controlling acamera comprising the steps of:selecting whether or not apre-illumination should be performed prior to a main illumination;performing a pre-illumination when it is selected that apre-illumination should be performed; starting to count a predeterminedtime in response to the start of the pre-illumination; and exposing afilm; wherein, when said selecting selects that said pre-illuminationshould be performed, said exposing is started after saidpre-illumination with a delay therefrom based on said predeterminedtime, and when said selecting selects that said pre-illumination shouldnot be performed, said exposing is started without said delay.
 19. Amethod of controlling an electronic flash apparatus comprising the stepsof:selecting whether or not a pre-illumination should be performed priorto a main illumination; receiving a start signal for starting apre-illumination when it is selected that a pre-illumination should beperformed; starting to count a predetermined time in response to thereceiving of the start signal; and starting to expose a film with adelay from said pre-illumination based on said predetermined time whensaid selecting selects that said pre-illumination should be performed,and starting to expose said film without said delay when said selectingselects that said pre-illumination should not be performed.